Refactor `SchemaDumper` to make it possible to adapter specific customization

[kamipo]

Currently SchemaDumper is only customizable for column options. But
3rd party connection adapters (oracle-enhanced etc) need to customizable
for table or index dumping also. To make it possible, I introduced
adapter specific SchemaDumper classes for that.

cc @yahonda

[yahonda]

Thanks for the pull request and update. I'm testing this pull request with Oracle enhanced adapter. So far I need to address "undefined method column_spec_for_primary_key"
https://gist.github.com/yahonda/18d4ae7317701188843a1d61e082a5c4

Let me have some more time to take a look at this pull request. I think I will have some questions.

[kamipo]

undefined method `column_spec_for_primary_key` is due to copying old table definition.

https://github.com/rsim/oracle-enhanced/blob/c463383d34cc113b0a394019cf89b0db076f2e52/lib/active_record/connection_adapters/oracle_enhanced/schema_dumper.rb#L124

All utility methods (column_spec and column_spec_for_primary_key as a public, and many internal private methods) that is used for schema dumping are moved in SchemaDumper and ColumnDumper is no longer included in the connection adapter.

[yahonda]

Thanks for pointing out. I overlooked that part. Now I have one failure.
The remaining part is how to consolidate these two namespaces. #30337 renames ColumnDumper to SchemaDumper.
Then it will conflict.

• ActiveRecord::ConnectionAdapters::OracleEnhanced::SchemaDumper
• ActiveRecord::ConnectionAdapters::OracleEnhanced::ColumnDumper

Will keep working on it.

[yahonda]

rsim/oracle-enhanced#1430 resolves all errors, failures and my questions. I think it looks good to me.

[yahonda]

cc @metaskills who maintains ActiveRecord SQL Server Adapter.

[kamipo]

SQL Server Adapter is only customized for column options, so it is easy to follow to this change.
I've created rails-sqlserver/activerecord-sqlserver-adapter#617.